Rotation Activated Downhole Orientation System and Method

ABSTRACT

A rotation activated orientation system  10  for a ground drill is operated by action of magnetic fields. The system  10  incorporates a magnetically operated orientator  12  having a free state where the orientator  12  provides a substantially instantaneous indication of a position of a reference bearing of a hole being drilled by the ground drill, and a locked state where the orientator maintains the indication. The system  12  also includes a magnetic actuator  14  operatively associated with the magnetically operated orientator  12 . When the rotational speed of the ground drill is greater than a threshold speed the magnetic actuator  14  supplies a magnetic field effective to place the orientator  12  in the free state. When the rotational speed of the drill is less than the threshold speed the magnetic actuator  14  does not supply a magnetic field effective to operate the orientator so that the orientator  12  reverts to or remains in the locked state.

TECHNICAL FIELD

A rotation activated downhole orientation system and method isdisclosed. The system and method may be used to determine theorientation of a core sample extracted from the ground by a core ordiamond drill.

BACKGROUND OF THE DISCLOSURE

Core sampling is used to enable geological surveying of the ground forvarious purposes including exploration, mine development and civilconstruction. Analysis of the material within the core sample providesinformation of the composition of the ground. Visual inspection of thecore also enables a geologist to map ore veins and boundaries betweendifferent types of materials. However, to do so it is necessary to knowthe orientation of the core relative to the ground from which it wascut.

Many types of core orientation systems are currently available. Some ofthese systems comprise a bottom orientator that provides an indicationof the bottom of the hole from which the core is extracted and anassociated trigger mechanism. One type of trigger mechanism operateswhen the core drill contacts a toe of the hole to freeze or capture thebottom orientation of the hole indicated by the bottom orientator. Analternate type of trigger mechanism operates by the act of breaking thecore from the ground.

The above reference to the background art does not constitute anadmission that the art forms a part of the common general knowledge of aperson of ordinary skill in the art. The above reference is also notintended to limit the application of the system and method as disclosedherein.

SUMMARY OF THE DISCLOSURE

Various aspects are disclosed of a system and method that enable theactuation or triggering of an orientator for a ground drill on the basisof rotational speed of the ground drill. The orientator provides anindication of the position of a reference bearing or location in or of ahole being drill by the core drill. The orientation of the coreextracted from the hole is the same as the orientation of the section ofthe hole from which the core is extracted.

Embodiments of the system rely on magnetic fields to switch theorientator between a free state in which the orientator is operable toprovide an instantaneous indication of the orientation of the hole inwhich it resides; and a locked state which locks or freezes theinstantaneous indication. In general terms, two embodiments of thesystem are disclosed for providing the magnetic field to actuate theorientator. In one embodiment a pump is operated by action of therotation of the drill to apply a pressurised fluid that in turn moves amagnet to a position where its magnetic field is effective to switch theorientator from its locked state to its free state. When the speed ofrotation of the drill drops below a threshold level, a bias mechanismoperates to move the magnet in an opposite direction away from theorientator so that its magnetic field is no longer effective on theorientator thereby enabling the orientator to revert to its lockedstate. In an alternate embodiment an electric motor is provided that isoperated by rotation of the drill. The electric motor produces a currentthat in turn drives an electromagnet. When the speed of the drill isgreater than a threshold speed the electric current causes thegeneration of a magnetic field of sufficient strength to switch theorientator from its locked state to its free state. When the speed ofthe drill falls below the threshold speed the resultant current flow isinsufficient to generate a magnetic field of a strength effective tohold the orientator in the free state. In that event the orientatorreverts to the locked state.

Those of ordinary skill in the art of core or diamond drilling willrecognise that a rotational speed of the drill string is 0 rpmimmediately prior to a core break. Thus in one embodiment the thresholdrotational speed of the drill may be set as 0 rpm. When the drill isbeing operated to drill a core the drill speed is greater than 0 rpm andthe magnetic actuator acts to urge or hold the orientator in the freestate. When the drill has stopped prior to a core break the drill speedis at the threshold speed of 0 rpm. The magnetic actuator no longerprovides an effective magnetic field and allows the orientator to revertto the locked state to freeze the indication of orientation immediatelyprior to core breaking. However in alternate embodiments the thresholdspeed may be greater than 0 rpm. In one example the threshold speedcould be up to 5 rpm. In this regard in embodiments of the system theorientator is biased in the absence of an external force to the lockedstate. Thus the magnetic actuator must overcome this bias to switch theorientator to the free state. According the threshold speed is justbelow the speed at which the magnetic field of the actuator becomeseffective to overcome this bias of the orientator.

In one aspect there is disclosed a rotation activated orientation systemfor a ground drill comprising:

-   -   a magnetically operated orientator having a free state where the        orientator provides a substantially instantaneous indication of        a position of a reference bearing or location in or of a hole        being drilled by the ground drill, and a locked state where the        orientator maintains the indication; and,    -   a magnetic actuator operatively associated with the magnetically        operated orientator wherein when the rotational speed of the        ground drill is greater than a threshold speed the magnetic        actuator supplies a magnetic field effective to place the        orientator in the free state, and when the rotational speed of        the drill is less than the threshold speed the magnetic actuator        does not supply a magnetic field effective to operate the        orientator so that the orientator reverts to or remains in the        locked state.

In one embodiment the rotation activated orientation system comprises atime delay system arranged to delay the orientator in reverting from thefree state to the locked state when the drill is rotating at a speedbelow the threshold speed.

In one embodiment the time delay system comprises a bleed path acting torestrict a flow rate of a fluid draining from a region which enables theorientator to move from a location corresponding to the free state to alocation corresponding to the lock state.

In one embodiment the fluid is oil and the time delay system is ahydraulic time delay system which provides the time delay by restrictingflow of oil through the bleed path.

In one embodiment the oil is transparent or translucent such that theindication provided by the orientator is visible through the oil.

In one embodiment the magnetic actuator comprises an electric machine ora fluid pump; and a coupling connected between the machine or the pumpand the drill to impart torque to the machine or the pump when the drillrotates.

In one embodiment when the magnetic actuator is the pump, the magneticactuator further comprises a magnet producing a magnetic field and acavity in which the magnet is able to move between a first positionwhere the magnet is spaced a distance from the orientator so that themagnetic field is not effective to place the orientator in the freestate; and a second position where the magnet is sufficiently close tothe orientator so that its magnetic field places the orientator in thefree state, and wherein the pump is operable to pressurise the fluid tomove the magnet from the first position to the second position.

In one embodiment the magnetic actuator comprises a bypass flow pathenabling fluid between the magnet and the orientator to flow from thecavity in response to the magnet moving from the first position towardthe second position.

In one embodiment wherein the magnetic actuator comprises a highpressure path providing fluid communication between an outlet of thepump and the cavity on a side of the magnet distant the orientatorwherein when the drill is rotating with a speed greater than thethreshold speed the pump provides pressurised fluid through the highpressure flow path to move the magnet toward the second position.

In one embodiment the magnetic actuator comprises a fluid return pathproviding fluid communication between the cavity and an inlet of thepump.

In one embodiment the bleed path is arranged to enable a continuouscirculating flow of fluid when the magnet is in the second position andwhile the drill is rotating at a speed greater than the threshold speed,wherein fluid flowing through the high pressure flow path and exertingpressure on the magnet holding the magnet in the second position isreturned to the pump via the bleed path.

In one embodiment the rotation activated orientation system comprises asump block disposed between the pump and the magnet, the sump blockdefining a fluid sump and being in direct fluid communication with thebleed path, the bypass path and the fluid return path.

In one embodiment the bleed path is formed in the sump block andprovides fluid communication between the fluid sump and the side of thecavity distant the orientator.

In one embodiment the sump block comprises a bore that forms a part ofthe high pressure flow path.

In one embodiment the rotation activated orientation system comprises abias mechanism acting to bias the magnet away from the second positionand toward the first position, the bias mechanism arranged so that whenthe drill is rotated at a speed greater than the threshold speed fluidpressure produced by the pump overcomes the bias mechanism and moves themagnet from the first position toward the second position; and when thedrill is operated at a speed less than the threshold speed the biasmechanism is operable to move the magnet in a direction from the secondposition toward the first position.

In one embodiment when the magnetic actuator is an electric machine theelectric machine comprises and electric generator arranged to generatean electric current when the drill is being rotated at a speed greaterthan the threshold speed.

In one embodiment the electric machine comprises an electro-magnetconnected to the electric generator, the electro-magnet arranged toproduce a magnetic field effective to place the orientator in the freestate when the drill is being rotated at a speed greater than thethreshold speed.

In one embodiment the orientator comprises a bias mechanism whichaccumulates potential energy when the orientator is being moved towardthe free state by action of the magnetic actuator and converts theaccumulated potential energy to kinetic energy when the drill is beingrotated at a speed less than the threshold speed to return theorientator to the locked state.

In embodiments of the rotation activated orientation system the bleedpath may operate as a fluid brake against action of the bias mechanismto restrict a rate of action of the bias mechanism in moving theorientator towards the locked position.

In a further aspect there is disclosed an orientation device comprisingat least one orientation element and an associated closed loop racehaving a central axis in which the orientation element is confined, therace comprising first and second clamp members between which theorientation element is located the first and second clamp members beingmovable relative to each other between a free position where the clampmembers are spaced sufficiently to enable the orientation element toroll about the axis within the closed loop race, and a locked positionwhere the clamping members are moved toward each other to contact theorientation element, and wherein at least one of the clamping members isresiliently deformable wherein when the orientator is in the lockedstate, the resiliently deformable clamping members deforms about theorientation element.

In one embodiment clamping members comprises a resilient washer.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thesystem and method as set forth in the Summary, specific embodiments willnow be described by way of example only with reference to theaccompanying drawings in which:

FIG. 1 is a longitudinal section view of a first embodiment of thesystem;

FIG. 2 is an enlarged view of a portion of the system shown in FIG. 1;

FIG. 3 is an enlarged view of a portion of the system shown in FIG. 1and indicating an initial flow of fluid for switching an associatedmagnetically operated orientator from a locked to free state;

FIG. 4 is a further view of the section of the system shown in FIG. 3 offluid now flowing in a steady state condition and holding themagnetically operated orientator in the free state;

FIG. 5 is a view of the portion of the system shown in FIG. 2 when thedrill is stationary and the magnetically operated orientator isswitching from the free state to the locked state;

FIG. 6 a is an isometric view from one angle of a sump blockincorporated in the embodiment of the system shown in FIGS. 1-5;

FIG. 6 b is an isometric view of the sump block of FIG. 6 a but from anopposite angle;

FIG. 7 is an isometric view of a magnetic coupling incorporated in theembodiment of the system shown in FIG. 1;

FIG. 8 is an isometric view of a spindle incorporated in the systemshown in FIG. 1;

FIG. 9 is a representation of a core marking system that may be used inconjunction with the orientation system shown in FIG. 1 for the purposesof providing an orientation mark on a core sample extracted by a coredrill in relation to which the orientation system is used;

FIG. 10 illustrates the core marking system coupled with a portion ofthe orientation system shown in FIG. 1;

FIG. 11 a is an isometric view from the bottom of a magnetic cradleincorporated in the core marking system shown in FIGS. 9 and 10;

FIG. 11 b is an isometric view of the magnetic cradle shown in FIG. 11a;

FIG. 11 c is an end view of the magnetic cradle shown in FIGS. 11 a and11 b;

FIG. 12 is a section view of a core tube assembly incorporating a secondembodiment of the orientation system;

FIG. 13 is an enlarged view of a magnetically operated orientatorincorporated in the embodiment of the system shown in FIG. 12 when in alocked state;

FIG. 14 is a representation of the magnetically operated orientator ofFIG. 13 in a free state;

FIG. 15 is a representation of the orientator of FIG. 14 illustrating afinal possible position when in the free state; and,

FIG. 16 is a representation of the orientator of FIGS. 13-15 whentransitioning from the free state back to the locked state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a pump embodiment of a rotation activated orientationsystem 10 (herein after “system 10”) for a ground drill (not shown). Thesystem 10 has a magnetically operated orientator 12 and an operativelyassociated magnetic actuator 14. The orientator 12 is disposed in alower housing 16. A down hole end 17 of the housing 16 is coupled to aninner core tube 18 (which is only partly shown). The magnetic actuator14 is coupled intermediate of the lower housing 16 and an upper housing20. The upper housing 20 is connected at an up hole end to a back endassembly (not shown). The back end assembly enables the system 10 to belowered and latched to a core barrel of the core drill and subsequentlyreleased and retrieved from the core barrel together with the inner coretube 18 and a core sample captured therein.

With particular reference to FIG. 2, the orientator 12 has casing 22with a cylindrical wall 24 and integrated radial wall 26 at one end, anda plug 28 that screws into an opposite end of the cylindrical wall 24.The casing is made of a transparent material so that its internal movingparts can be seen when lower housing 16 is separated from the screwcoupling 64. An inside surface of the cylindrical wall 24 is formed withthree axially spaced apart races 30 a, 30 b and 30 c (hereinafterreferred to in general as “races 30”). The races 30 are in the form ofgrooves which have a concave profile. Interleaved with the races 30 is aset of grooves 32 a-32 c (hereinafter referred to in general as “grooves32”). The races 30 are configured to partially seat and receiverespective orientation elements in the form of balls 34 a-34 crespectively (hereinafter referred to in general as “balls 34”). Each ofthe grooves 32 seat respective O-rings 36 a-36 c (hereinafter referredto in general as “O-rings 36”).

A “T” shaped plunger 38 extends coaxially within the casing 22. Theplunger 38 is formed with a stem 46 having an increased diameter cap 40at an end nearest the radial wall 26. The cap 40 has an outer diametermarginally smaller than an inner diameter the cylindrical wall 24. Thisprovides a small clearance and fluid flow path to enable pressureequalisation on opposite sides of the disc as the plunger 38 slidesaxially within the casing 22. A permanent magnet 44 is disposed betweenthe cap 40 and the radial wall 26. The magnet 44 is able to move orslide axially within the up hole portion 42. Optionally the magnet 44can be attached to the cap 40.

The stem 46 has a constant outer diameter. A transverse through hole 48is formed near a down hole end 50 of the stem 46. Additionally, a hole52 is formed from the end 50 and extends axially along the stem 46 tothe transverse hole 48.

Four spacer rings 54 a-54 d (hereinafter referred to in general as“spacer 54” or “spacers 54”) are co-axially arranged on the plunger 38about stem 46. The spacers 54 are separated by respective elasticallydeformable washers 56 a-56 c (hereinafter referred to in general as“washers 56”). Specifically, washer 56 a separates or is otherwisedisposed between spacers 54 a and 54 b; washer 56 b separates or isotherwise located between spacers 54 b and 54 c; and washer 56 cseparates or is otherwise disposed between the spacers 54 c and 54 d.

A bias mechanism in the form of a metal coil spring 58 is located aboutthe stem 46 between the spacer 54 d and the end 50. Further, the spring58 is retained in a circumferential rebate 60 formed in the plug 28. Thespring 58 is arranged to apply bias to the spacers 54 and consequentlyto the plunger 38 in a direction pushing the plunger 38 toward theradial wall 26. Thus the spring acts to bias the orientator toward thelocked state. The plug 28 is formed with an axially cavity 62. Theplunger 38 and cavity 62 are relatively dimensioned so that the plunger38 can slide axially further into the cavity 62.

In the configuration shown in FIG. 2, the orientator 12 is in its lockedstate with the spring 58 biasing the plunger 38 toward the radial wall26 so that there balls 34 are clamped between the washers 56 and O-rings36. It will also be seen that a space or gap exists between the end 50and the bottom wall of the cavity 62. When the orientator 12 is in thefree state (as shown in FIG. 4) the plunger 38 is moved axially in adown hole direction so that the balls 34 are free to roll in theirraces. Additionally the end 50 is closer to or indeed contacts thebottom wall of the cavity 62.

The orientator 12 threadingly engages an inner circumferential wall of ascrew coupling 64. The screw coupling 64 is integrally formed at theuphole end of the inner core tube 18. The lower housing 16 screws ontothe screw coupling 64.

The interior of the outer casing 22 may be filled with a lighttransparent oil or at least translucent liquid. The balls 34 are made ofa specific gravity greater than that of the oil. Therefore provided theorientator is in its free state and assuming that the system 10 isinclined from the vertical, the balls 34 will sink in the oil to alowest point of their respective races 30. This results in theorientator 12 being a bottom of a hole orientator.

The depth of the races 30 and the outer diameter of the spacers 54 arearranged so that the balls 34 are confined in axial direction. That is,while the balls 34 many roll or otherwise move about their respectiveraces 30 they are unable to roll out in an axial direction from theirrespective races 30.

The washers 56 and O-rings 32 co-operate to form respective clamps thateither hold the balls 34 in place or release the balls 34 enabling themto roll in their respective races 30 about the stem 46. Thus the O-rings32 and the washers 56 constitute first and second clamping members ofthe clamp. One or both of the claiming members can be resilientlydeformable. In one embodiment at least the washers are resilientlydeformable.

The orientator 12 is in the free state when a washer 56 and itscorresponding O ring 32 are sufficiently spaced apart to notsimultaneously contact the corresponding ball 34 to the extent to impederolling of a ball 34 with a corresponding race 30. This configuration isdepicted in FIG. 4. However, when the orientator 12 is in the lockedstate for example is shown in FIG. 2, the balls 34 are contacted onopposite sides by its respective washer 56 and O-ring 36. This achievedby action of the spring 58 pushing the spacer rings and plunger 42 hardup against the end wall 26.

The washers 56 of each clamp are configured so that when the orientatoris in the locked state parts of the washers in contact with the ballresiliently deform about the ball by action of the spring. This forms adepression in the washers that cradle the balls. This provides greatercontact area between a ball 34 and washer 56 than that in the eventwhere the washer is not resilient deformable under the action of thespring.

With particular reference to FIGS. 1, 2 and 3, the magnetic actuator 14in this embodiment comprises a magnetic drive gear pump 70 and magnets72. The magnets 72 are axially moveable within a cavity 74. Magneticdrive gear pumps are readily available. One example of current use ofsuch pumps is in the metering of liquid medicaments. The pump 70 isprovided with a high pressure outlet 76 and lower pressure inlet port78. The gears of the pump 70 are rotated by way of a magnetic coupling80 which in turn is coupled to a spindle 82 (FIG. 1). The spindle 82 iscoupled to the back end assembly and rotates about its longitudinal axiswhen a corresponding drill rotates. The upper housing 20, the lowerhousing 16 and orientator 12 are rotationally decoupled from the spindle82 by way of a swivel arrangement 84. The magnets 44 and 72 are arrangedto have like poles facing each other. That is the magnets 44 and 72produce magnetic fields that mutually repel.

The pump 70 is provided with a body 86 which houses the pump gears. Themagnetic actuator 14 further includes a sump block 88 and an optionaloil reservoir 90. The magnets 72 are retained within a piston 92 that isable to slide in axially direction within the cavity 74. The cavity 74is defined between a dividing wall 94 formed in the lower housing 16 andthe sump block 88. The sump block 88 is clamped onto the opposite end ofthe cavity 74 when the magnetic actuator 14 is attached to the lowerhousing 16. A return spring 96 acts between the dividing wall 94 and thepiston 92/magnets 72 biasing the magnets 72 away from the magnet 44 ofthe orientator 12.

A high pressure flow path 98 extends from the pump outlet 76 and throughthe sump block 88 to provide high pressure fluid to a side of themagnets 72/piston 92 distant the orientator 12. The path 98 comprises abore 100 formed in a body of the magnetic actuator 14 and a bore 102formed in the sump block 88. The pump block 88 is further provided withan oil sump 104 and bleed path 106. The bleed path 106 extends through aplug 108 of the sump block 88 which fits in to the cavity 74. Further,the bleed path 106 provides fluid communication between sump 104 and aside of the magnets 72/piston 92 distant the orientator 12.

A bypass flow path 110 provides fluid communication between the cavity74 and sump 104. The flow path 110 comprises in combination a bore 112formed in the body of the lower housing 16 and which extends in anaxially direction, and circumferential feed groove 114 formed on theinside wall of the cavity 74. A hole 116 formed in the sump block 88provides fluid communication between the bypass flow path 110 and thesump 104. Oil is returned from the sump 104 to the inlet port 78 viareturn path 118 which is formed as an axially extending bore in the bodyof the actuator 14.

The piston 92 is formed with a head 120 of an outer diameter marginallysmaller than the inner diameter of the cavity 74. The head 120 is formedwith a circumferential groove which seats a sealing ring 122. At an endof the piston 92 opposite the head 120 a cavity 124 is provided forseating and retaining the magnets 72. The return spring 96 is arrangedto bias the piston 92 away from the orientator 12.

With particular reference to FIGS. 1, 7 and 8, the magnetic coupling 18comprises a cup like structure 126 which is configured to fit over anend portion of the pump 70. The cup like structure 126 is formed with aplurality of recesses 128 which seat drive magnets 130. A connectionpost 132 extends axially from the cup like structure 126 in a directionway from the orientator 12. A hexagonal shaped hole 134 is formedaxially in the post 132 and receives a hex key 136 formed at an end ofthe spindle 82. A circumferential groove 138 is formed in the post 132near but inboard of its free end. The groove 138 seats a circlip 140which holds the post 132 within bearings 142 seated in the upper end ofthe body of the actuator 14.

The spindle 82 extends through and is able to rotate axially within aspindle bearing 144 which threadlingly engages upper end of the upperhousing 20. The spindle 82 also extends through upper and lower thrustbearings 146 and 148 respectively. The thrust bearing 146 and 148 arelocated adjacent opposite side of the spindle bearing 144. The thrustbearing 146 is also located adjacent a shut off valve 150. The shut offvalve 150 is seated about the spindle 82 between the thrust bearing 146and a stop 152 of the spindle 82.

A spring 154 acts between the thrust bearing 148 and a nut 156 threadedonto the spindle 82. The spring 154 acts to bias the spindle 82 in adirection toward the orientator 12 to maintain engagement of the hex key136 in the hex hole 134. To this end, the spindle 82 is able to slide inan axial direction to operate the shut off valve 150.

The operation of the system 10 will now be described in detail.

As previously explained the system 10 is attached to a back end assemblyand lowered by a wire line into a core drill. An inner core tube 18 isattached to an opposite end of the system 10. FIGS. 1 and 2 depict thelocked state of the system 10 which occurs when the rotational speed ofthe drill is at or below a threshold speed. In this example thethreshold speed is 0 rpm. When the drill is at this speed (i.e. is notrotating) the pump 70 is not operating to pump oil from its outlet 76.Thus no fluid pressure is exerted on the magnets 72/piston 92. Ratherthe return spring 96 biases the magnets 72/piston 92 away from theorientator 12. Also the spring 60 is biasing the plunger 38 toward thewall 26 of the casing 22. This pushes the spacer rings 54 hard upagainst the cap 40 of plunger 38. This in turn brings the washers 56 intheir closest proximity to the O-rings 36 clamping the balls 34 therebetween and preventing them from rotating in their races 30. Theorientator 12 is accordingly in the locked state with the position ofthe balls 34 being locked or fixed by clamping action of the washers 56and O-rings 36 on opposite sides of the balls 34. Due to the distancebetween the magnets 44 and 72 the magnetic field of the magnets 72 hasno effect or at least has no effective interaction with the magneticfield of the magnet 44 for the purposes of pushing the plunger 38 in adown hole direction to release the balls 34 and the orientator 12 fromthe locked state.

When the drill rotates for example when operating to drill a coresample, torque is transferred via the spindle 82 to the magneticcoupling 80. The upper body 20, lower body 16 and the orientator 12 arerotationally decoupled from the drill by virtue of the swivel 84. Therotation of the magnetic coupling 80 operates the pump 70 causing fluidto be pumped from the high pressure port 76 through the high pressurepath 98 to a region in the cavity 74 between the piston head 120 and theplug 108. Provided the flow rate is greater than the return flow ratethrough the bleed path 106 and the pressure of the fluid on the piston92 is greater than that applied in a reverse direction by the spring 96,then the piston 92/magnets 72 will slide in an axial direction towardthe orientator 12 compressing the spring 96. This flow rate may beconsidered to be the operational flow rate. The operational flow ratewill occur when the drill rotates at a speed greater than the thresholdspeed. As previously exemplified this may be 0 rpm. However thethreshold speed may be greater than 0 rpm. For example this may be 1-5rpm. The threshold speed is set by design and is influenced by severalfactors including but not limited to the diameter of the bleed path 106and spring constant of the spring 96.

As the magnets 72 move toward the orientator 12, oil within the cavity74 between the piston head 120 and the wall 94 flows through the bypassflow path 110 and hole 116 into the sump 104 to be subsequentlycirculated through the pump 70 via the return flow path 118. Thiscirculation and movement of oil is depicted in FIG. 3. Eventually themagnets 72 will move to within a distance where its magnetic field willbe effective in repelling the field the magnet 44. Now the magneticfield from the magnets 72 is able to interact with the field of themagnet 44 repelling the magnet 44 and causing the magnet 44 togetherwith the plunger 38 to move in a down hole direction away from themagnets 72. This releases the balls 34 enabling them to rotate in theirrespective races.

Eventually, the pumping of oil by the pump 70 through the high pressurepath 98 forces the magnets 72/piston 92 to the bottom of the cavity 74and abutting the wall 96. During continued rotation of the drill a smallamount of oil is recirculated through the bleed path 106 to the sump 104and return flow path 118. Thus the continued rotation of the drillmaintains the operation of the pump 70 and fluid pressure on the magnets72 holding the orientator 12 in the free state.

When the inner core tube 18 is full and it is necessary to break thecore sample from the ground, the rotation of the drill is stopped. Thisresults in the ceasing of rotation of the magnetic coupling 80 andconsequently the pump 70 ceases pumping oil and applying pressure to themagnets 72/piston 92. As a consequence, the return spring 96 is now ableto move or slide the magnets 72 axially away from the orientator 12 andtoward the plug 108. This is achieved by way of a slow flow of oilthrough the bleed path 106. The bleed path 106 is of a relatively smalldiameter so that the flow of oil is relatively slow and thus the motionof the magnets 72 is slow. Oil which passes through the bleed path 106to the sump 104 is then caused to flow back into the cavity 74 throughthe bypass flow path 110 as shown in FIG. 5.

Due to the slow return motion of the magnets 72 the effect on the magnet44 diminishes slowly resulting in the slow up hole motion of the plunger38. This produces a time delay for the orientator 12 to switched back toits locked state from the time the drill speed is at or below itsthreshold speed. The time delay provides the balls 34 with time tosettle to the lowest point within their respective races 30 and therebyprovide an accurate indication of the bottom of the hole. The delay maymitigate effects of vibrations and linear movement of the drill afterrotation has ceased and in preparation for a core breaking operation. Inone example, the time delay for the orientator 12 to switch back to itslock position may be for example a time in the range of thirty secondsto one minute from the time the drill speed drops to or below thethreshold speed. In this way the bleed path 106 may be seen as formingat least in part a time delay system 160.

The pump 70 acts as a flow restriction and indeed a shut off valve inrelation to fluid flowing from the inlet 78 to the outlet 76 when pump70 is not rotating. This assists in restricting oil flow when the drillis not rotating. As such the pump when not rotating may also beconsidered as forming part of the time delay system.

The time delay system 160 in this embodiment is a hydraulic time delaysystem as it operates by restricting flow of a fluid through the bleedpath 106. More particularly the time delay system 160 restricts the flowof fluid draining from a region 77. In this embodiment fluid may be inthe form of a liquid. The liquid may have a viscosity greater thanwater. Further the liquid may have lubricating properties and/or provideprotection against corrosion. The liquid may take the form of oil.Examples of oils that may be used include but are not limited toparaffin oil; engine oil and hydraulic oil. The region 77 in thisembodiment is between the piston 92 and the sump block 88. Draining ofthe fluid from the region 77 enables the orientator 12 to move from adown hole location corresponding to the free state (FIG. 4) to an uphole location corresponding to the locked state (FIG. 2). The orientator12 is enabled to move between these locations to effect the change fromfree state to locked state by virtue of the piston 92 and magnets 72moving axially away from the magnet 44 of the orientator 12.

As will be understood if the drill speed where to increase to be abovethe threshold speed then the orientator 12 will revert to or at leasttend towards the free state. This provides a self-setting or re-settingfeature where for example the drill speed fell below the threshold speedprior to a core breaking operation and subsequently speed up back to thenormal drilling speed.

The system 10 can then be returned to the surface with the inner coretube 18.

Once returned to the surface, the bottom of hole indication provided bythe orientator 12 can be transferred to a core sample 170 held in theinner core tube 18 by use of a core marking system 180 depicted in FIGS.9-11 c. The core marking system 180 comprises a magnetic cradle 182, anorientation guide 184, and a core marking guide 186.

The magnetic cradle 182 comprises a block 188 having a planar base 190of a rectangular shape and two opposed upright planar surfaces 192 a and192 b. Two further side walls 194 a and 194 b are convexly curved andextend between the side walls 192 a and 192 b. A portion of the block188 opposite the base 190 is formed with a channel 196 having a planarbottom 198 and opposite outwardly diverging planar walls 200 a and 200b. One or more magnets 202 are embedded in each of the side walls 200 a,200 b and the base 190.

The orientation guide 184 comprises a tube 204 having an inner diameterwhich is able to fit with light to moderate interference onto the outercasing 22 of the orientator 12. A longitudinal window or slot 206 isformed in the tube 204 and is dimensioned so that when the orientationguide 184 is fitted onto the orientator 12 each of the three orientationballs 34 can be viewed through the window 206 assuming that the balls 34are substantially aligned. One end of the tube 204 is provided with aknob 208 in which is fitted a spirit level 210.

The core marking guide 186 comprises a tube 212 which is opened at oneend 214. The tube 212 has an inner diameter which is dimensioned toengage and fit over the inner core tube 18 with light to moderateinterference. The light to moderate interference fitting of theorientation guide 184 and core marking guide 186 is to enable therespective guides to be fitted on and removed by hand but maintainsufficient grip so as to maintain their position in the absence of beingmanipulated by hand.

A longitudinal slot 216 is formed in the tube 212 from an intermediatelocation 218 inboard of the opening 214 and extending to a radialsemicircular face 220 at an opposite end of the tube 212. A marking hole222 is formed in the face 220 in alignment with the slot 216. A semicylindrical extension 224 projects axially of the tube 212 and is fittedwith a spirit level 226.

The manner of use of the core marking system 180 will now be described.Once the core breaking operation has been completed and the system 10has been retrieved the lower housing 16 together with the actuator 14and upper housing 20 is unscrewed or otherwise decoupled from the innercore tube 18 and the orientator 12. This is achieved by unscrewing thethread about the screw coupling 64 at an uphole end of the inner coretube 18. Thus the orientator 12 remains with the inner core tube 18 andthe casing 22 and orientation balls 34 are now exposed and visible.

The magnetic cradle 182 is placed on a ferromagnetic (for example steel)bench. Due to the magnets 202 in the bottom wall 190 the cradle 182 ismagnetically held on the bench. Next the inner core tube 18 is seated inthe valley 196 with the orientator 12 extending from one side of thecradle 182 and the core sample 170 extending from an opposite side. Themagnets 202 in the inclined walls 200 a and 200 b hold the rotationaland translational position of the core tube 18 until changed by manuallyrotating or translating the tube 18 against the magnetic attractionforce applied by the magnets 202.

The position of the balls 34 is fixed or locked by action of theorientator 12. When placing the inner core tube 18 on the cradle 182 theballs 34 should be visible and in particular approximately in a verticalplane. The orientation guide 184 is now fitted over the outer casing 22and manipulated so that the orientation balls 34 are visible through theslot 206. The position of the spirit level 208 is now viewed. If thespirit level 208 does not indicate a horizontal plane then the innercore tube 18 is manually rotated within the valley 196 so that thespirit level 210 indicates that it is now lying in a horizontal plane.The core marking guide 186 is now fitted on an opposite end over aportion of the core sample 170 and onto the inner core tube 18. The coremarking guide 186 is rotated about the inner core tube 18 until thespirit level 226 indicates that it is lying in a horizontal plane. Thusnow the two spirit levels 226 and 210 indicate that the slots 216 and206 are aligned.

In the present embodiment, the balls 34 are locked by the system 10 whenin use to indicate the location of the bottom of a hole from which thecore sample 170 is extracted. By using a marker pencil or a scribe, amark is placed through the slot 216 on the circumferential portion ofthe core sample 170 extending from a core lifter case 228 of the innercore tube 18. This mark will be in the form of a line if the pencil orscribe is moved along the slot 216. Additionally, if desired or requireda further bottom of the hole mark can be placed on a radial face of thecore sample 170 by inserting a pencil or marking scribe through the hole222.

Now that an indication of the bottom of the hole has been transferredonto the core sample 170 the orientation guide 184 and core markingguide 186 can be removed and the core sample 170 extracted from theinner core tube 18. The inner core tube 18 and orientator 12 can then bereconnected to the remaining parts of the system 10 and reused toorientate a subsequent core sample.

FIG. 12 illustrates a further embodiment of the system designated assystem 10′. The features of the system 10′ that are identical to thoseof the system 10 are denoted with the same reference numbers. Thefeatures however which differ but function in a similar manner areindicated with the same reference number as for the system 10 but withthe addition of the prime symbol (′).

The substantive differences between the systems 10 and 10′ lie in the:form of the actuator 14′; and, various components of the orientator 12′to provide the return time delay when the rotational speed of the drilldrops below the threshold speed. The magnetic actuator 14′ in thisembodiment comprises an electric generator 230 and an electromagnet 232which together produce a magnetic field to repel the magnet 44 when therotational speed of the drill is greater than the threshold speed. Thegenerator 230 has a drive shaft 234 at an uphole end which may be formedwith a hexagonal hole (not shown) of the same configuration as the hole134 of the coupling 80 in the first embodiment. This hole receives thehex key 136 of the spindle 82. Engagement of the hexagonal hole 134 andthe key 34 enables axial motion of the spindle 82 when the shut offvalve 150 is activated and subsequently released. This action is exactlythe same as in the first embodiment.

The electromagnet 232 comprises an outer magnetic coil 236 and anelectro-magnet core 238. When the drill is rotated the electricgenerator 230 generates a current that is fed to the coil 236 to inducea magnetic field in the core 238. The current circulates in a directionso that lines of magnetic flux of the electro magnet 232 at a down holeend produce a pole of the same polarity as the facing end of the magnet44. An electronic control chip 240 of the magnetic actuator 14′regulates the current/voltage to the coil 236. In particular, theelectronic control chip 240 limits the maximum current delivered to thecoil 236. This is provided as a safety mechanism to minimise the risk ofburning out the coil 236 in the event that the rotational speed of thedrill for some reason substantially exceeds the expected normal drillingspeed.

The orientator 12′ in the system 10′ comprises an outer casing 22′ madeof a transparent plastics material and of generally the same shape andconfiguration as that of the orientator 12. However an additional race242 is formed in the inner circumferential surface of the casing 22′ forseating a floating ball 244. The ball 244 has a specific gravity greaterthan that of the oil in which it is immersed and will float to a highestposition in a hole containing the system 10′ when the system 10′ isinclined from the vertical. The ball 244 however is not clamped and isalways able to freely move within the race 242.

The plunger 38′ comprises a stem 46′ having an axially extending blindhole 246 which terminates at an intermediate location 248 along thelength of the stem 46′. The purpose of the hole 246 is simply to reducethe weight of the stem 46′. The open end of the hole 246 is closed by acap 40′ which is provided with a seat for holding the magnet 44. Axiallyextending holes 247 are formed in the cap 40′. The stem 46′ is alsoformed with a transverse through hole 48 and a hole 52 extending axiallyfrom the end 50 to the hole 48 as in the plunger 38. However in thisembodiment a one way or non-return valve 250 is seated in the hole 52.The valve 250 enables a flow of oil in a direction from the end 50 upthrough the hole 52 and into the transverse hole 48. However the valve250 prevents a flow of oil in a direction from the hole 48 into the hole52. A lower end of the cavity 62′ is formed with a circumferentialshoulder 257 that acts as a stop to limit for the travel of the plunger38′ when being stoked down by the magnetic field of the actuator 14′.The shoulder is created by tapering the bottom portion of the interiorsurface of the cavity 62′ to form a conical surface 259.

The time delay in the return stroke of the plunger 38′, which changesthe state of the orientator from the free state to the locked state, isachieved by the provision of a time delay system 160′ that is housedwithin the plug 28′ of the orientator 12′ and interact with the plunger38′ in its return stroke to the locked position.

The plug 28′ is of a different configuration to that of the orientator12 and has an up hole portion 256 that progressively reduces in outerdiameter in an up hole direction. This forms an annular flow path 258between the inner surface of the casing 22′ and the outercircumferential surface of the up hole portion 256. A transverselyextending through hole 260 is formed in the up hole portion 256. A bleedpath 106′ extends in an axial direction from the hole 260 to axialcavity 62′ formed in the plug 28′. An adjustable needle valve 264 ishoused in a cavity 266 in the plug 28′ and is provided with a taperedneedle point 268 that extends into the bleed path 106′. The position ofthe needle point 268 in the bleed paths 106′ can be controlled by ascrew disc 270 that threadingly engages the cavity 266. A spring 272 isretained about the needle valve 264 and maintains the position of theneedle point 268 in the bleed path 106′ in accordance with the positionof the screw disc 270. By turning the screw disc 270 either clockwise oranticlockwise the position of the needle point 268 in the bleed path106′ can be controlled thereby controlling the amount of oil that canflow through the bleed path 106′.

The operation of the system 10′ will now be described in detail. Whenthe rotational speed of the drill is at or below the thresholdrotational speed the generator 230 produces current but not sufficientto generate a magnetic field of a strength that is effective to interactwith the magnet 44 of the orientator 12′ for the purpose of changing itsstate from its rest or initial locked state where the balls 34 areclamped between washers 56 and O-rings 36. Again, this threshold speedcan be 0 rpm or a higher speed. However when the drill is in operationdrilling a core sample, the rotational speed of the drill is above thethreshold speed. In this event the electric generator 230 generates avoltage and current sufficient such that the electromagnet 232 producesa magnetic field of an intensity effective to interact with the magneticfield of the magnet 44 to push the plunger 38′ in a down hole directionagainst the bias of spring 58.

FIG. 14 depicts the axial motion of the plunger 38′ in the downholedirection caused by the magnetic field applied by the electromagnet 232.As the plunger 38′ moves in this direction the washers 56 are moved awayfrom the balls 34 thereby allowing them to freely roll in theirrespective races 30 under the influence of gravity. The non-return valve250 allows oil within the cavity 62′ to flow through the hole 52 andhole 48 thereby preventing a hydraulic lock which may otherwise resistthe downward motion of the plunger 38′. Additionally, a flow of oiloccurs through the holes 247 formed in the cap 40′. This allows anequalisation of oil pressure on opposite sides of the cap 40′.

The non-return valve 250 is of a conventional construction having avalve ball/head that is lightly biased by a spring (not shown) onto avalve seat (not shown). When the plunger 38′ is moved in a downholedirection as indicated in FIG. 14, the oil is able to push the ballagainst the light spring opening the non-return valve. However once theflow of oil ceases, the valve spring is able to return the valveball/head back on its seat thereby closing the valve.

FIG. 15 depicts the configuration of the orientator 12′ after the drillhas been rotating at a speed greater than the threshold speed for arelatively short period of time such as but not limited to 20-30seconds. The plunger 38′ is moved to its maximum extent in the down holedirection with the down hole end 50 of the stem 46 abutting thecircumferential shoulder 257 formed in the cavity 62′ by the taperedside walls 259.

As drilling continues, the plunger 38′ is maintained in the positionshown in FIG. 15. However there is now no flow of oil within the housing22′. The bias mechanism, i.e. spring 58 is now in its most compressedstate and has accumulated potential energy from the kinetic energy ofthe previously moving plunger 38′.

When the speed of the drill drops to or below the threshold speed, forexample when the drill stops rotating prior to performing a corebreaking operation, the magnetic field provided by the electromagnet 232no longer exists. Thus the plunger 38′ is now urged to return to thelocked position by action of the spring 58. The spring 58 releases itsaccumulated potential energy which is converted to kinetic energy inmoving the plunger 38′ toward locked state. The spring 58 pushes thespacer rings 54 a-54 d hard up against the cap 40′ and consequentlybiases the plunger 38′ and the washers 56 in an up hole direction. Thisaction returns the orientator 12′ back to the locked state. During thisreturn action the time delay system 160′ operates to enable a flow ofoil back into the cavity 62′ with a time delay. Without this oil flowthe plunger 38′ may be hydraulically held in the free state due to thenon-return valve 250 preventing a flow of oil in a direction from thehole 48 through the hole 52 back into the cavity 62′.

The flow of oil into the cavity 62′ via the time delay system 160′ isshown by arrows 275 in FIG. 16. The time delay system 160′ acts to allowoil to flow back into the cavity 62′ via the annular flow path 258, hole260 and bleed path 106′. The amount of oil admitted through the bleedpath 106′ is controlled to provide a time delay for switching of theorientator 12′ back to the locked state. The flow of fluid back to thecavity 62′ acts as a fluid brake against the release of the potentialenergy of the spring 58 thus providing the time delay. This time delaymay for example be in the order of thirty seconds to one minute. As withthe previous embodiment, the time delay provides time for the balls 34to fall to the lowest position in their races 30 prior to the corebreaking action. As with the embodiment of FIGS. 1-5 the time delaysystem 160′ also acts to restrict the flow of fluid draining from aregion 77′. Here the region 77′ is the volume of the casing 22′ bar thecavity 62′. The bleed path 106′ provides restricted flow of fluid fromthe region 77′ into the cavity 62′ thereby enabling the orientator 12′to move from a down hole location corresponding to the free state (FIG.15) to an up hole location corresponding to the locked state (FIG. 13).

The floating ball 244 is always free to rotate or roll within its race242 and thus will always position itself at the highest location withinthe race 242 commensurate with the inclination of the system 10′.

Once the system 10 has been retrieved the location of the bottom of thehole from which the core sample was extracted can be marked in exactlythe same way as described herein before above using the core markingsystem 180. The provision of the floating ball 244 provides anadditional level of confidence or accuracy in provision of the marking.Specifically, when the inner core tube 18 has been rotated within themagnetic cradle 182 so that the balls 34 are in alignment and both thespirit levels 220 and 226 are indicative of respective horizontalplanes, the floating ball 244 should also be in alignment with the balls34 and the slots 206 and 216.

However the provision of the floating ball 244 provides an alternate andslightly simpler way of marking the location of the bottom of the hole.This method still utilises the cradle 182 but does not require theorientation guide 184. In effect the floating ball 244 within the race242 acts in a manner identical to the spirit level 210. Thus all that isrequired is that once the inner core tube 18 is placed within the cradle182, inner core tube 18 needs to be rotated so that the ball 244 is inalignment with the balls 34. When this occurs, a line that passesthrough the balls 34 and 244 is representative of the bottom of the holeand thus marking or transferring such a line onto the core sample 170via the core marking slot 216 and/or hole 222 provides a record on thecore 170 itself of the position of the bottom of the hole.

Now that embodiments of the invention have been described in detail itwill be apparent to those skilled in the art that numerous modificationsand variations can be made without departing from the basic inventiveconcepts. For example the orientators 12 and 12′ are described ascomprising three rolling balls, however the number of rolling ballsgreater than one is not critical to the operation of the embodiment,only to the degree of confidence of the bottom of hole indication. Alsoin the embodiment comprising the pump 70, the fluid is described as oil,however the fluid can be other liquids or indeed could be a gas. Furtherwhile the embodiments are described in the context of core drilling andcore orientation their application extends to at least hole orientationirrespective of whether or not a core sample is being extracted. Allsuch modifications and variations together with others that would beobvious to those of ordinary skill in the art are deemed to be withinthe scope of the disclosed orientation system and method the nature ofwhich is to be determined from the above description and the appendedclaims.

1. A rotation activated orientation system for a ground drillcomprising: a magnetically operated orientator having a free state wherethe orientator provides a substantially instantaneous indication of aposition of a reference bearing or location in or of a hole beingdrilled by the ground drill, and a locked state where the orientatormaintains the indication; and, a magnetic actuator operativelyassociated with the magnetically operated orientator wherein when therotational speed of the ground drill is greater than a threshold speedthe magnetic actuator supplies a magnetic field effective to place theorientator in the free state, and when the rotational speed of the drillis less than the threshold speed the magnetic actuator does not supply amagnetic field effective to operate the orientator so that theorientator reverts to or remains in the locked state.
 2. The rotationactivated orientation system according to claim 1 comprising a timedelay system arranged to delay the orientator in reverting from the freestate to the locked state when the drill is rotating at a speed belowthe threshold speed.
 3. The rotation activated orientation systemaccording to claim 2 wherein the time delay system comprises a bleedpath acting to restrict a flow rate of a fluid draining from a regionwhich enables the orientator to move from a location corresponding tothe free state to a location corresponding to the lock state.
 4. Therotation activated orientation system according to claim 3 wherein thefluid is oil and the time delay system is a hydraulic time delay systemwhich provides the time delay by restricting flow of oil through thebleed path.
 5. The rotation activated orientation system according toclaim 4 wherein the oil is transparent or translucent such that theindication provided by the orientator is visible through the oil.
 6. Therotation activated orientation system according to claim 3 wherein themagnetic actuator comprises an electric machine or a fluid pump; and acoupling connected between the machine or the pump and the drill toimpart torque to the machine or the pump when the drill rotates.
 7. Therotation activated orientation system according to claim 6 wherein whenthe magnetic actuator is the pump, the magnetic actuator furthercomprises a magnet producing a magnetic field and a cavity in which themagnet is able to move between a first position where the magnet isspaced a distance from the orientator so that the magnetic field is noteffective to place the orientator in the free state; and a secondposition where the magnet is sufficiently close to the orientator sothat its magnetic field places the orientator in the free state, andwherein the pump is operable to pressurise the fluid to move the magnetfrom the first position to the second position.
 8. (canceled)
 9. Therotation activated orientation system according to claim 7 wherein themagnetic actuator comprises a high pressure path providing fluidcommunication between an outlet of the pump and the cavity on a side ofthe magnet distant the orientator wherein when the drill is rotatingwith a speed greater than the threshold speed the pump providespressurised fluid through the high pressure flow path to move the magnettoward the second position.
 10. The rotation activated orientationsystem according to any one of claims 7 wherein the magnetic actuatorcomprises a fluid return path providing fluid communication between thecavity and an inlet of the pump.
 11. The rotation activated orientationsystem according to claim 7 wherein the bleed path is arranged to enablea continuous circulating flow of fluid when the magnet is in the secondposition and while the drill is rotating at a speed greater than thethreshold speed, wherein fluid flowing through the high pressure flowpath and exerting pressure on the magnet holding the magnet in thesecond position is returned to the pump via the bleed path.
 12. Therotation activated orientation system according to claim 11 comprising asump block disposed between the pump and the magnet, the sump blockdefining a fluid sump and being in direct fluid communication with thebleed path, the bypass path and the fluid return path.
 13. The rotationactivated orientation system according to claim 12 wherein the bleedpath is formed in the sump block and provides fluid communicationbetween the fluid sump and the side of the cavity distant theorientator.
 14. (canceled)
 15. The rotation activated orientation systemaccording to claim 7 comprising a bias mechanism acting to bias themagnet away from the second position and toward the first position, thebias mechanism arranged so that when the drill is rotated at a speedgreater than the threshold speed fluid pressure produced by the pumpovercomes the bias mechanism and moves the magnet from the firstposition toward the second position; and when the drill is operated at aspeed less than the threshold speed the bias mechanism is operable tomove the magnet in a direction from the second position toward the firstposition.
 16. The rotation activated orientation system according toclaim 15 wherein the bleed path operates as a fluid brake against actionof the bias mechanism to restrict a rate of action of the bias mechanismin moving the orientator towards the locked position.
 17. The rotationactivated orientation system according to claim 6 wherein when themagnetic actuator is an electric machine the electric machine comprisesand electric generator arranged to generate an electric current when thedrill is being rotated at a speed greater than the threshold speed. 18.The rotation activated orientation system according to claim 17 whereinthe electric machine comprises an electro-magnet connected to theelectric generator, the electro-magnet arranged to produce a magneticfield effective to place the orientator in the free state when the drillis being rotated at a speed greater than the threshold speed.
 19. Therotation activated orientation system according to claim 17 wherein theorientator comprises a bias mechanism which accumulates potential energywhen the orientator is being moved toward the free state by action ofthe magnetic actuator and converts the accumulated potential energy tokinetic energy when the drill is being rotated at a speed less than thethreshold speed to return the orientator to the locked state.
 20. Therotation activated orientation system according to claim 19 wherein thebleed path operates as a fluid brake against action of the biasmechanism to restrict a rate of action of the bias mechanism in movingthe orientator towards the locked position.
 21. An orientation devicecomprising at least one orientation element and an associated closedloop race having a central axis in which the orientation element isconfined, the race comprising first and second clamp members betweenwhich the orientation element is located the first and second clampmembers being movable relative to each other between a free positionwhere the clamp members are spaced sufficiently to enable theorientation element to roll about the axis within the closed loop race,and a locked position where the clamping members are moved toward eachother to contact the orientation element, and wherein at least one ofthe clamping members is resiliently deformable wherein when theorientator is in the locked state, the resiliently deformable clampingmembers deforms about the orientation element.
 22. The orientationdevice according to claim 21 wherein one of the clamping memberscomprises a resilient washer.